<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    #app{
        width:600px;
        margin: 40px auto;
        text-align: center;
    }
</style>
<body>
    <script src="/js/vue.js"></script>
    <div id ="app">
      <h2>当前计数器值为：{{num}}</h2>
      <counter v-on:counter-add="num++"></counter>
    </div>
    <script>
        Vue.component('counter',{
            template:'<button @click="add">计数器</button>',
            methods:{
                add:function(){
                    this.$emit('counter-add')
                }
            }
        })
       let app =new Vue({
         el:"#app",
         data:{
           num:0
         },
         methods:{
            handleAdd:function(){
                this.num++
            }
         }
       })
    </script>  
</body>
</html>